Contrasting response of European forest and grassland energy exchange to heatwaves

• Published in: Nature geoscience Vol. 3; no. 10; pp. 722 - 727
• Main Authors: Teuling, Adriaan J, Seneviratne, Sonia I, Stöckli, Reto, Reichstein, Markus, Moors, Eddy, Ciais, Philippe, Luyssaert, Sebastiaan, van den Hurk, Bart, Ammann, Christof, Bernhofer, Christian, Dellwik, Ebba, Gianelle, Damiano, Gielen, Bert, Grünwald, Thomas, Klumpp, Katja, Montagnani, Leonardo, Moureaux, Christine, Sottocornola, Matteo, Wohlfahrt, Georg
• Format: Journal Article Web Resource
• Language: English
• Published: London Nature Publishing Group UK 2010; Nature Publishing Group
• Subjects: 704/106; 704/158/2453; 704/158/2454; Agriculture & agronomie; Agriculture & agronomy; anemometer (co)sine response; balance closure; Climate; Climate system; climate-change; deforestation; Earth and Environmental Science; Earth science; Earth Sciences; Earth System Sciences; Energy; Environmental sciences & ecology; Evaporation; Extreme heat; flux measurements; Forests; Geochemistry; Geology; Geophysics/Geodesy; Grasslands; Heat; Heat waves; heat-wave; Heating; impact; Life Sciences; Moisture content; Radiation; Sciences de l’environnement & écologie; Sciences du vivant; Soil moisture; Soil water; Solar radiation; summer; Temperature; transpiration; Water balance; Water use; water-vapor; Netherlands; Belgium; Europe; Italy; France; Switzerland; Germany
• ISSN: 1752-0894; 1752-0908; 1752-0908
• DOI: 10.1038/ngeo950

Recent European heatwaves have raised interest in the impact of land cover conditions on temperature extremes. At present, it is believed that such extremes are enhanced by stronger surface heating of the atmosphere, when soil moisture content is below average. However, the impact of land cover on the exchange of water and energy and the interaction of this exchange with the soil water balance during heatwaves is largely unknown. Here we analyse observations from an extensive network of flux towers in Europe that reveal a difference between the temporal responses of forest and grassland ecosystems during heatwaves. We find that initially, surface heating is twice as high over forest than over grassland. Over grass, heating is suppressed by increased evaporation in response to increased solar radiation and temperature. Ultimately, however, this process accelerates soil moisture depletion and induces a critical shift in the regional climate system that leads to increased heating. We propose that this mechanism may explain the extreme temperatures in August 2003. We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates the impact of the most extreme heat and/or long-lasting events.
European heatwaves have raised interest in the impact of land-cover conditions on temperature extremes. Analyses of observations from an extensive network of flux towers in Europe reveal a difference in the response of forests and grassland to extreme or long-lasting heat.